Remember when you were a kid and you'd knock on walls trying to uncover hidden staircases? Of course, you do. These five homes make good on that childhood dream with carefully-concealed private spaces.

No matter the month, it's never too cold or too early to start planning for major eco-impact. From urban rooftop gardens to living surfaces that help homeowners save on energy costs, here you'll find plenty of ideas for the final (green) frontier: the green roof.

In our October issue (on newsstands September 10), we tour developer Doug Burgum's green rooftop deck filed with local grasses and plants, LED-illuminated privacy screens, and a natural-gas fireplace. Stay tuned by checking back on September 5 for a better view!